ImportanceVisual impairment (VI) and blindness continue to be major public health problems worldwide. Despite previously published studies on VI in Chinese and other racial/ethnic populations, there are no data specific to Chinese American adults.

ObjectivesTo determine the age- and sex-specific prevalence and causes of VI and blindness in adult Chinese Americans and to compare the prevalence to other racial/ethnic groups.

Design, Setting, and ParticipantsIn this population-based, cross-sectional study of 10 US Census tracts in the city of Monterey Park, California, 4582 Chinese American adults 50 years and older underwent complete ophthalmologic examinations, including measurement of presenting and best-corrected visual acuity (BCVA) for distance using the Early Treatment Diabetic Retinopathy Study protocol from February 1, 2010, through October 31, 2013.

Main Outcomes and MeasuresAge-specific prevalence and causes of VI and blindness for presenting and BCVA.

ResultsOf the 5782 eligible adults, 4582 (79.2%) completed an in-clinic eye examination. Of the 4582 participants, most were born in China (3149 [68.7%]), female (2901 [63.3%]), and married (3458 [75.5%]). The mean (SD) age was 61 (9) years. The prevalence of presenting VI was 3.0% (95% CI, 2.5%-3.5%), with 60.0% of this prevalence being attributed to uncorrected refractive error. The overall age-adjusted prevalence for VI (BCVA of ≤20/40 in the better eye) was 1.2% (95% CI, 0.9%-1.5%). The overall age-adjusted prevalence of blindness (BCVA of ≤20/200 in the better-seeing eye) was 0.07% (95% CI, 0%-0.2%). The prevalence of VI and blindness was higher in older Chinese Americans compared with younger. The primary causes of VI were cataracts and myopic retinopathy; the primary cause of blindness was myopic retinopathy.

Conclusions and RelevanceThe prevalence of VI in Chinese Americans is similar to that of non-Hispanic white and Latino individuals in the United States and similar to or lower than the prevalence previously reported for Chinese adults from non-US studies. The prevalence of blindness is lower than that noted in other US or non-US studies. Myopic retinopathy is a frequent cause of VI and blindness in Chinese Americans that has not been commonly observed in other racial/ethnic groups. Because myopia frequently develops at a young age, Chinese Americans should be educated regarding the importance of regular screening of preschool and school-aged children to reduce the development and progression of myopia.

Introduction

Visual impairment (VI) and blindness continue to be major public health problems in the United States and worldwide. Currently, more than 4 million persons in the United States older than 40 years are visually impaired or blind.1 A report2 by the World Health Organization (WHO) estimates that 285 million people are visually impaired worldwide; 39 million of these people are blind. Economic consequences of VI and blindness in adults include greater medical costs, greater number of days for informal care, and decreased use of health services.3 Medical and informal care costs for VI and blindness are estimated at $5.5 billion annually, with an additional $10.5 billion per year when including loss of quality-adjusted life-years.3,4

Despite previously published studies on VI in Chinese and other racial/ethnic populations in the United States5- 7 and outside the United States,8- 15 there are no data specific to Chinese American adults. According to the 2010 US Census Brief,16 Asians are the fastest-growing racial group in the United States, and Chinese Americans are the largest subgroup of Asian Americans. Because VI and blindness are a significant public health concern, it is important to have current data specific to the various segments of the diverse US population. Various stakeholders can then use these data in developing local and national programs for eliminating correctable VI and blindness and reducing irreversible vision loss.

To our knowledge, the Chinese American Eye Study (CHES) is the largest, most comprehensive population-based study of eye disease among persons 50 years and older of Chinese ancestry living in the United States, providing precise estimates of VI and blindness prevalence. In this article, we report (1) the age- and sex-specific prevalence of VI and blindness among Chinese Americans, (2) the causes of VI and blindness among Chinese Americans, and (3) comparisons of the age-adjusted prevalence of VI and blindness among Chinese Americans with other population-based studies of persons of Chinese ancestry and other racial/ethnic groups inside and outside the United States.

Key Points

Question What are the prevalence and causes of visual impairment and blindness among Chinese Americans?

Findings The prevalence of visual impairment and blindness was lower than reported in cohorts of non-Hispanic white and Latino individuals living in the United States but varied in Chinese cohorts outside the United States. Myopic retinopathy was a frequent cause of visual impairment and blindness and more common than observed in other racial/ethnic groups.

Meaning The results of this study suggest roles for education and community outreach regarding cataract and myopic retinopathy, which are leading causes of visual impairment in the Chinese American community.

Methods

Study Population

CHES is a population-based study of self-identified Chinese Americans 50 years and older living within 10 US Census tracts in Monterey Park, California. Details of the study design and sampling methods are outlined elsewhere.17 Briefly, participants were identified using a door-to-door census of all dwelling units performed in all targeted tracts. Eligible residents were invited to complete a home survey and a comprehensive eye examination at the local eye examination center. Written informed consent was obtained during enrollment from February 1, 2010, through October 31, 2013. The Institutional Review Board/Ethics Committee of the Los Angeles County+USC Medical Center approved the protocol and informed consent forms for this study. CHES complies with current Health Insurance Portability and Accountability Act regulations. All data were deidentified.

Ocular Examination

Vision was measured for each eye with presenting correction (if any) at 4 m using standard Early Treatment Diabetic Retinopathy Study protocols with a modified distance chart transilluminated with a chart illuminator (Precision Vision).18 Presenting distance visual acuity (VA) was measured for both eyes, the left eye, and the right eye with existing refractive correction. If the participant could not read 55 letters at 4 m in either eye (equivalent to Snellen fraction 20/20), an automated refraction was performed using the Humphrey Automatic Refractor (Carl Zeiss Meditec), followed by subjective refraction. After refraction, the eye was retested to measure the best-corrected VA (BCVA). If the participant was unable to read 20 letters at 4 m (equivalent to Snellen fraction 20/100), measurement and subjective refraction were performed at 1 m. An LEA chart was used for participants unable to read standard charts. The VA score was calculated using the total number of letters read correctly by the participant and then converted into logMAR.

Definition of VI

There are 2 major definitions of VI. First, VI and blindness can be defined based on presenting binocular VA. This definition includes the burden of VI owing to both uncorrected refractive error (URE) and other causes. In our study, we used the US criterion of presenting binocular VA of less than 20/40. Second, VI and blindness can be defined based on the BCVA in the better-seeing eye. This definition excludes the burden of VI from URE and identifies the burden of VI from various eye diseases.

There are 2 major VA criteria to characterize VI and blindness based on BCVA. The US criterion defines VI as a BCVA of 20/40 or less in the better-seeing eye. The VI severity is defined as mild (20/40–20/63), moderate (20/80–20/160), or severe (≤20/200). Other population-based studies5,7,14 have used this criterion. The WHO defines VI as a BCVA of less than 20/63 but greater than or equal to 20/400. Non-US studies8- 13,15 and US studies6,7 have used this criterion.

Definition of Blindness

Blindness was defined using the US and WHO criteria. The US criterion of blindness is a BCVA of 20/200 or less in the better-seeing eye. Most US studies5- 7 and non-US studies8,14,15 have used this criterion. The WHO defines blindness as a BCVA of 20/400 or less in the better-seeing eye. Population-based studies6- 15 around the world have used this criterion.

Determination of the Cause of VI and Blindness

After reviewing all participants’ medical records, independent investigators reached consensus diagnoses using standard clinical criteria. The investigators reviewed all clinical examination findings, lens gradings, visual field assessments, and fundus photographs for each participant with VI or blindness and made a final determination of the cause for each eye. If the examining ophthalmologist and clinical reviewer did not agree, the principal investigator (R.V.) adjudicated the cause of VI. They assigned the primary cause to the condition expected to produce the greatest limitation of vision.

Statistical Analysis

Prevalence of VI and blindness was calculated as the ratio of the number of participants with VI or blindness to the total number of participants with complete data. Estimates were presented with 95% CIs. Sex- and age-specific prevalence (50–59, 60–69, 70–79, and ≥80 years) was presented. The χ2 and Cochran-Mantel-Haenszel tests were used to evaluate statistically significant differences by age and sex. Direct standardization was applied to calculate age-adjusted prevalence using the 2010 US Census standard population for Asians. All analyses used SAS statistical software, version 9.3 (SAS Institute Inc). P < .05 was considered statistically significant.

Results

Study Cohort

Of the 5782 eligible adults, 4582 (79.2%) completed an in-clinic eye examination. Participation was consistent across all age groups. Of the 4582 participants, most were born in China (3149 [68.7%]), female (2901 [63.3%]), and married (3458 [75.5%]). The mean (SD) age was 61 (9) years.

CHES participants were similar in age to the overall population of Chinese living in the United States (2180 [47.6%] CHES participants vs 1 070 000 [44.0%] US Chinese were 50–59 years old) and more likely to be female (2901 [63.3%] of CHES participants vs 1 260 000 [51.8%] US Chinese).19 The proportion of CHES participants with 12 or more years of education was slightly lower than that of Chinese living in the United States (3090 [67.4%] CHES participants vs 1 870 000 [76.9%] US Chinese).

Compared with participants who completed the clinical examination, eligible nonparticipants were similar in age (mean age, 63 vs 61 years), more likely to be current smokers (103 [12.1%] vs 304 [6.6%]; P < .001), and less likely to have 12 or more years of education (491 [57.9%] vs 3090 [67.4%]; P < .001). There were no differences in income, health insurance, or vision coverage; percentage born outside the United States; or self-reported history of diabetes, high blood pressure, cataracts, or macular degeneration.

Prevalence of VI

The overall age-adjusted prevalence of VI for presenting binocular VA using the US criterion was 3.0% (95% CI, 2.5%-3.5%). The prevalence of presenting VI was higher in older individuals (P for trend < .001). The prevalence based on the WHO criterion was lower (Table 1).

The age-adjusted prevalence of VI based on the BCVA in the better-seeing eye (US definition) was 1.2% (95% CI, 0.9%-1.5%). The prevalence was higher in each successively older age group (P for trend <.001) for all severity levels (P for trend < .001), and no sex-specific differences were observed. The prevalence based on WHO criteria was lower (Table 2).

Prevalence of Blindness

The age-adjusted prevalence of blindness for presenting binocular VA using the US criteria was 0.08% (95% CI, 0.0%-0.2%). The prevalence was low, and the numbers in each age strata were too small to reveal trends. There were no sex-specific differences after adjusting for age. The results for the WHO criterion were similar (Table 1).

The age-adjusted prevalence of blindness using BCVA in the better-seeing eye was 0.07% (95% CI, 0.0%-0.2%) using the US criterion (Table 2). No sex-specific differences in prevalence of blindness were observed (P = .80). The prevalence of blindness was higher for each successively older age group based on the worse eye using both the US and WHO criteria (P < .001).

Primary Causes of VI and Blindness

When using presenting VA based on the US criterion (<20/40 to >20/200), the leading cause of VI (70.3%) was URE (Table 3). The most frequent causes of VI based on BCVA using the US criterion (<20/40 to >20/200) were cataract (75 [42.9%]) and myopic retinopathy (23 [13.1%]). When compared with BCVA, 414 cases (70.3%) of presenting VI were explained by URE. Myopic retinopathy was the primary cause of blindness, using both the US (4 [40.0%]) and WHO criterion (1 [33.3%]), based on very small numbers of cases.

Comparison With Other Studies

By comparing our findings with the age-specific and age-adjusted prevalence of VI observed in other population-based studies, we noted similar patterns of VI in Chinese Americans. However, the prevalence of blindness was lower in Chinese Americans than in persons of Chinese ancestry living outside the United States (Table 4 and Table 5).

When presenting VA was used, the leading cause of VI (414 [70.3%]) was URE (Table 3). The age-specific prevalence of any VI (best-corrected, better-seeing eye, US criterion) ranged from 0.8% in 50- to 59-year-old Chinese Americans to 25.8% in those 80 years and older. The age-specific prevalence of blindness (best-corrected, better-seeing eye) ranged from 0.05% in 50- to 59-year-old Chinese Americans to 0.3% in those 80 years and older.

Comparison With Other US Studies

The age-standardized prevalence of VI (US criterion) revealed similar prevalence across racial/ethnic groups, ranging from the highest in Latino individuals (1.4%)7 followed by Chinese Americans (1.2%) and then non-Hispanic white individuals (0.9%)5 (Table 4). Latino adults in the Los Angeles Latino Eye Study (LALES)7 had a slightly higher prevalence of VI (best-corrected, better-seeing eye) across all age groups when compared with Chinese Americans when using the US criterion. The overall, age-adjusted prevalence of VI in African American individuals in the Baltimore Eye Survey (BES)6 was slightly higher (0.6%) compared with CHES (0.2%) using the WHO criterion. The age-adjusted prevalence of VI in non-Hispanic white individuals in BES was similar to that of CHES (0.3% and 0.2%, respectively).

The age-adjusted prevalence of blindness was lower in Chinese Americans (0.07%) than in African American (0.5%), non-Hispanic white individuals (0.3%), and Latino (0.2%) individuals in the United States.5- 7 African American individuals from BES had higher rates of blindness across all age strata compared with CHES participants (Table 5)14; non-Hispanic white adults in the Beaver Dam Eye Study5 and CHES had a similar prevalence of blindness in the age groups of 60 to 69 years and 70 to 79 years. However, the prevalence of blindness was higher for non-Hispanic white individuals older than 80 years in the Beaver Dam Eye Study and BES compared with Chinese Americans.5,6

Comparison With Other Non-US Studies

Non-Hispanic white individuals in the Blue Mountains Eye Study (BMES)14 had a lower prevalence of VI (best-corrected, better-seeing eye) compared with CHES participants across all age groups when using the US criterion (Table 4). The overall age-adjusted prevalence in non-Hispanic white individuals from the BMES was 0.7% compared with 1.2% for CHES participants. Afro-Caribbean individuals from the Barbados Eye Study15 had the highest age-adjusted prevalence of VI overall (1.8%) and across all age strata compared with non-US individuals and CHES participants.

For individuals 60 years and older, the prevalence of VI was higher in adult persons from Shihpai, Taiwan, than in Chinese Americans.8 However, the overall age-adjusted prevalence was similar in both studies (0.3% vs 0.2%, respectively). For this age group based on the WHO criterion, the prevalence of VI for CHES participants was lower than reported for persons of Chinese ancestry from any non-US urban8- 10,13 or rural11- 13 population-based eye studies (Table 4).

On the basis of the US criterion, the overall age-adjusted prevalence of blindness in the Shihpai Eye Study and CHES were similar (0.09% and 0.07%, respectively).8 Non-Hispanic white adults from the BMES had a similar overall age-adjusted prevalence of blindness to Chinese Americans based on both the US and WHO criteria (0.07% BMES vs 0.07% CHES [US criterion] and 0.04% BMES vs 0.02% CHES [WHO criterion]).14 Afro-Caribbean individuals from the Barbados Eye Study had a higher prevalence of blindness across all age groups compared with Chinese Americans7,15 (Table 5).

Discussion

CHES is a large, population-based study of eye disease among Chinese adults 50 years and older living in the United States (Monterey Park, California). It was designed to provide robust, population-based prevalence estimates of VI and blindness. When presenting VA was used, the leading cause of VI (70.3%) was URE, whereas the leading cause of VI based on the best-corrected, better-seeing eye was cataract followed by myopic retinopathy. The age-specific prevalence of any VI (best-corrected, better-seeing eye, US criterion) in Chinese Americans ranged from 0.8% in 50- to 59-year-old persons to 25.8% in those 80 years and older. Age-specific prevalence of blindness (best-corrected, better-seeing eye) ranged from 0.05% in 50- to 59-year-old Chinese Americans to 0.3% in those 80 years and older.

The most common underlying cause of presenting VI in Chinese Americans was URE (70.3%), suggesting that vision screening and refractive correction will eliminate a high proportion of cases. In addition, URE can interfere with a person’s ability to complete normal, daily, vision-related tasks and decrease the perception of well-being.20,21 Thus, timely detection and management of VI will enable Chinese Americans, particularly those who are older, to maintain greater independence and quality of life.

Similarly, refractive error is the leading cause of VI in various racial/ethnic groups across the United States and the world.20,21 In the Salisbury Eye Evaluation (SEE), 34% of VI in white individuals and 23% of VI in black individuals were a result of URE,20 whereas BES found that 66% of VI in white individuals and 57% of VI in black individuals were a result of URE.6 The proportions of presenting VI attributable to URE in Latinos in Los Angeles and Arizona were 75% and 73%, respectively.21

Although the causes of best-corrected VI vary in frequency across population-based studies8- 11,13,20,22- 24 of different racial/ethnic groups, the most common cause was cataracts. In Chinese Americans, cataracts account for 43% of best-corrected VI, followed by myopic retinopathy (13%), macular pucker (9%), and macular degeneration (9%). In studies of persons with Chinese ancestry outside the US, cataracts were also the most common cause: 37% in the Beijing Eye Study,13 42% in the Shihpai study,8 44% in the Liwan Eye Study,9 48% in the Handan Eye Study,11 and 60% in the Tanjong Pagar Eye Study.10 Similarly, the most common cause of best-corrected VI in various racial/ethnic groups in the United States was cataract: 38% of white and 34% of black individuals in BES,6 40% of white and 47% of black individuals in SEE,20 49% of Latino individuals in LALES,23 and 47% of Latino individuals in Proyecto VER.24

In CHES, the leading causes of blindness based on the US definition were myopic retinopathy (40%), cataract (10%), and macular degeneration (10%). In the Beijing,13 Handan,11 and Liwan9 studies of persons of Chinese ancestry, the leading cause of blindness was cataracts (38%, 32%, and 45%, respectively); in the Shihpai Eye study,8 the leading cause was other retinal diseases (38%). The most frequent cause in the Tanjong Pagar Eye Study10 was glaucoma (60%) followed by cataract (20%). In Chinese Americans, cataracts were not the leading cause of blindness because Chinese Americans may have better access to cataract surgery than their counterparts in rural China. In Chinese Americans, myopic retinopathy was a leading cause of blindness and VI, reflecting the irreversible nature of this condition.

A major strength of this analysis is the inclusion of population-based data using a large number of adults (N = 4582), a high participation rate (79.2%), and standardized clinical methods for assessing VA. CHES also reports age-specific and age-adjusted prevalence rates to allow for appropriate comparison with other populations.

The CHES population is mostly composed of Mandarin-speaking immigrants from mainland China. Although there are small differences, we believe the Chinese Americans included in this study are representative of Chinese Americans in the United States. However, caution is warranted when extrapolating these estimates to Chinese populations of different geographic or genetic heritages, which may contribute to differences in the burden of VI and blindness. Therefore, age-specific or age-standardized estimates should be used to compare prevalence differences across Chinese populations.

Conclusions

CHES is a large and comprehensive study of eye disease in persons of Chinese ancestry older than 50 years that provides precise estimates of age- and sex-specific prevalence and the most common causes of VI and blindness. To our knowledge, it is the first large, population-based study of VI, blindness, and eye disease of Chinese Americans in the United States. Our data suggest that Chinese Americans in CHES have a prevalence of VI similar to that of non-Hispanic white individuals and Latino individuals in the United States and a similar or lower prevalence than Chinese adults from non-US studies. However, the prevalence of blindness is lower in Chinese Americans than in non-Hispanic white individuals or Latino individuals in the United States or Chinese from non-US studies. Similar to other racial/ethnic groups, URE was the most common cause (70.3%) of presenting VI in CHES. The primary cause of best-corrected VI was cataracts, whereas the most common cause of blindness was myopic retinopathy. Further studies are needed to carefully evaluate the role of environmental and lifestyle factors and genetic susceptibility that may contribute to the lower prevalence of blindness in Chinese Americans.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Funding/Support: This work was supported by grant EY-017337 from the National Eye Institute, National Institutes of Health, Bethesda, Maryland (Dr Varma, principal investigator), and an unrestricted departmental grant from Research to Prevent Blindness, New York, New York.

Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and the decision to submit the manuscript for publication.